1. Field of the Invention
The present invention relates to a PON station side apparatus, a PON uplink line communication method, a PON uplink line communication program, and a program recording medium, and in particular to a PON station side apparatus that enables different communication speeds to coexist in a PON uplink line, a PON uplink line communication method, and a program recording medium.
2. Description of the Related Art
A PON system connects an aggregation station and multiple terminal apparatuses of subscribers' homes by an optical fiber network in which one optical fiber branches to multiple optical fibers via an optical coupler, and this PON system attracts much attention as the core technology of FTTH (Fiber to the Home) technology.
However, the technique described above has problems as shown below.
In an EPON (Ethernet passive optical network), which is a PON system based on the Ethernet (R) technique, the communication method is specified in accordance with the IEEE802.3 standard. At first, the Ethernet communication speed that is to be the base of this communication standard was 1 Gbps, which is the communication speed of the Gigabit Ethernet. However, use of a new communication speed, such as 10 Gigabit Ethernet, has started, and there is a possibility that both speeds may coexist in an uplink line.
When multiple kinds of communication speeds are allowed to coexist in the uplink line, an aggregation station side terminating apparatus, that is, a PON station side apparatus OLT (optical line terminal) requires a receiving function that is compatible with the multiple kinds of communication speeds. In JP-2007-243285-A, a technique is proposed in which a PON system specifies the transmission start time and the transmission speed for transmitted data in an uplink line, from a PON station side apparatus OLT to a terminal side terminating apparatus, that is, a PON terminal apparatus ONU (optical network unit), and sets the receiving circuit of the PON station side apparatus OLT to perform a receiving operation suitable for data at the specified transmission speed.
However, in the technique described in JP-2007-243285-A, when data are transmitted in a state in which communication speeds coexist by wavelength division multiplexing or time division multiplexing, from multiple terminal apparatus side terminating apparatuses, that is, PON terminal apparatuses ONUs (optical network units), there may be a case in which it is not possible to sufficiently cope with the transmission. That is, though it is generally assumed that wavelength division multiplexing or time division multiplexing is adopted in a case in which different communication speeds are allowed to coexist in an uplink line, there is a possibility that, in such a case, the PON station side apparatus OLT cannot perform a normal data receiving function.
For example, in the case of realizing a data receiving operation in a PON station side apparatus OLT while allowing different communication speeds to coexist in an uplink line by using time division multiplexing, it is assumed to adopt a technique of applying bandwidth allocation by using a DBA (dynamic bandwidth allocation), module which is a time division multiplexing technique for a PON system, as described in JP-2007-243285-A. However, in the case of the configuration like that of JP-2007-243285-A, since the OLT receives data that have different communication speeds and according to different communication methods when in a time-division multiplexed state in which use of the bandwidth allocation occurs through use of a DBA module, whether effective or ineffective data has been received cannot be determined. Therefore, there is a possibility that, for example, the OLT erroneously reconfigures such data as has been received at a wrong timing as effective data.